This 2-year project will conduct exploratory research on the causes and consequences of cocaine abuse among patients in methadone maintenance treatment programs (MMTPs), in order to develop an improved psychosocial treatment model for cocaine-abusing patients. The research will examine the differences between methadone patients who are and are not abusing cocaine, and will derive a treatment-relevant classification of cocaine-abusing patients. This typology will be based on the pattern and severity of patients' cocaine abuse, precursors of the abuse, patients' current level of functioning, and their readiness and suitability for a given treatment alternative. The project will identify how MMTPs are responding to cocaine abuse and what treatment strategies and control techniques are being used by counselors, nurses, administrators and physicians. The research will examine which of these existing individual or clinic-wide cocaine treatment techniques seem to be effective or ineffective with what types of patients. Unmet cocaine treatment needs will also be identified. This will lead to the formulation of a Differential Treatment Model for cocaine abuse that will serve as a useful guide for MMTPs nationally. Four MMTPs will participate in the study, selected purposively to maximize diversity of program treatment environments. An entry cohort and a current treatment sample in each program, consisting of a total of 390 patients (250 cocaine users, 140 controls) will be studied longitudinally over 9 months. Patients will be classified by cluster analysis, and patient characteristics and treatment-related variables will be correlated with case outcomes using multiple regression analysis. Data collection will include: in-depth patient interviews, TLC and EMIT urinalysis, a psychiatric status scale, case record reviews, staff interviews, and ethnographic methods such as field observations and informal interviews.